"Some of those concerns are based for that time period and much has changed, but does more work need to be done? Do we need to continue to move forward and evolve our approach? Obviously. We're still having earthquakes,” Matt Skinner, spokesperson for the Oklahoma Corporation Commission, said.

The EPA points out that Oklahoma allowed some restricted wells to return to normal operations.

Bob Jackman said he is glad the EPA is taking more action.

"The state of Oklahoma is injecting the equivalent of 517 Empire State buildings per year underground," he said.

Jackman says there are still more than 700 wells injecting into the Arbuckle formation-- a seismic hot spot.

"It's like you've got a major underground fire and somebody is saying well we've almost stopped pouring gasoline on it, but we're still allowing a little bit,” Jackman said.

The OCC says they have a good relationship with the EPA and the state's work understanding and limiting injection wells is not done.